Basis of Presentation and Significant Accounting Policies - Schedule of Revenues from Third Party Payers, Uninsured and Other Payers (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Revenues From Third Party Payers [Line Items]
Revenues	$ 19,849	$ 19,161	$ 59,188	$ 56,087
Revenues ratio from third party payers	100.00%	100.00%	100.00%	100.00%
Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 2,925	$ 2,728	$ 8,910	$ 8,426
Revenues from third party payers, Ratio	14.70%	14.20%	15.10%	15.00%
Managed Medicare [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 3,530	$ 3,306	$ 10,462	$ 9,957
Revenues from third party payers, Ratio	17.80%	17.30%	17.70%	17.80%
Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 1,765	$ 1,783	$ 5,998	$ 4,413
Revenues from third party payers, Ratio	8.90%	9.30%	10.10%	7.90%
Managed Medicaid [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 961	$ 949	$ 2,897	$ 2,727
Revenues from third party payers, Ratio	4.80%	4.90%	4.90%	4.90%
Managed Care and Insurers [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 9,574	$ 9,267	$ 27,671	$ 27,432
Revenues from third party payers, Ratio	48.30%	48.40%	46.70%	48.80%
International (Managed Care and Insurers) [Member]
Revenues From Third Party Payers [Line Items]
Revenues from third party payers	$ 492	$ 484	$ 1,482	$ 1,390
Revenues from third party payers, Ratio	2.50%	2.50%	2.50%	2.50%
Other [Member]
Revenues From Third Party Payers [Line Items]
Revenues	$ 602	$ 644	$ 1,768	$ 1,742
Other, Ratio	3.00%	3.40%	3.00%	3.10%